Solvent Extraction of Vanadium with α-Benzoin Oxime

The solvent extraction of vanadium by a chloroform solution of α-benzoin oxime was investigated. The most favorable condition for the extraction has been found in the pH rang of 1.8 to 3.0 in sulfate or chloride buffer solutions, but with better extraction efficiency when sulfate was used. A solution of 2×10^?2 M α-benzoin oxime in chloroform was used, and 1×10^?4 to 2×10^?2 M vanadium(V) was extracted favorably in about 89% yield by a single extraction, and in about 97% yield by a double extraction. The effects of shaking time, concentration of α-benzoin oxime, and diverse ions have also been investigated. Vanadium(V) can be readily extracted without interference in the presence of copper(II), aluminum(III), iron(III), silver(I), zirconium(IV), and chromium(III).     

Solution representations of percentage change problems: the pre-service primary teachers’ mathematical thinking and reasoning

Solution representations can reveal how problem solvers communicate mathematical thinking and reasoning in problem-solving process. The present study examined the solution representations used by 20 pre-service teachers for the percentage change problems. The pre-service teachers were invited to solve a combination of simple and complex percentage change problems. The score for the majority of simple problems was 75% or above, but the score for the complex problems was below 75%. The highest percentage error occurred when the pre-service teachers encountered a percentage greater than 100% in the percentage change problems. Irrespective of their level of mathematics qualifications, the equation approach demonstrating two-step problem-solving process was the predominant strategy adopted by the pre-service teachers. The equation approach imposes low cognitive load and, therefore, is more accessible and efficient than the unitary approach. A few pre-service teachers used the unitary approach. The findings indicate that the pre-service teachers possessed relevant mathematical knowledge for percentage change problems. Furthermore, the inclusion of the equation approach in mathematics textbooks would provide an alternative perspective regarding the teaching and learning of percentage change problems.     

Extending the working calibration ranges of four hexachlorocyclohexane isomers in gas chromatography-electron capture detector by radial basis function neural network

A radial basis function neural network (RBFNN) method was developed for the first time to model the nonlinear calibration curves of four hexachlorocyclohexane (HCH) isomers, aiming to extend their working calibration ranges in gas chromatography-electron capture detector (GC-ECD). Other 14 methods, including seven parametric curve fitting methods, two nonparametric curve fitting methods, and five other artificial neural network (ANN) methods, were also developed and compared. Only the RBFNN method, with logarithm-transform and normalization operation on the calibration data, was able to model the nonlinear calibration curves of the four HCH isomers adequately. The RBFNN method accurately predicted the concentrations of HCH isomers within and out of the linear ranges in certified test samples. Furthermore, no significant difference (p > 0.05) was found between the results of HCH isomers concentrations in water samples calculated with RBFNN method and ordinary least squares (OLS) method (R² > 0.9990). Conclusively, the working calibration ranges of the four HCH isomers were extended from 0.08-60 ng/ml to 0.08-1000 ng/ml without sacrificing accuracy and precision by means of RBFNN. The outstanding nonlinear modeling capability of RBFNN, along with its universal applicability to various problems as a “soft” modeling method, should make the method an appealing alternative to traditional modeling methods in the calibration analyses of various systems besides the GC-ECD.     

Locked nucleic acid/DNA chimeric aptamer probe for tumor diagnosis with improved serum stability and extended imaging window in vivo

As promising molecular probes for in vivo tumor imaging, aptamers without modification remain problematic due to insufficient serum stability and unabiding imaging window. To address this problem, a novel locked nucleic acid (LNA)/DNA chimeric aptamer probe was developed through proper LNA incorporation and supplemented 3′-3′-thymidine (3′-3′-T) capping. TD05, a DNA aptamer against lymphoma Ramos cells, being used as the model, a series of modification strategies were designed and optimized with different positions, numbers and combinations. It was revealed that the combined use of LNA and 3′-3′-T had a synergistic effect, and with the increase of LNA substitution in stem region, the serum stability of TD05 was gradually enhanced while its affinity and specificity were perfectly maintained to Ramos cells. Particularly, TD05.6 with 7-base pair-LNA substitution exhibited the significantly elevated detection stability half-life from ∼0.5 h of TD05 to 5–6 h of TD05.6 for target cells in serum. Moreover, a much slower clearance rate in tumor-bearing mice was also observed for TD05.6, thus leading to the greatly extended tumor imaging window from <150 min of TD05 to >600 min of TD05.6. This strategy might be of great potentials to generate more aptamer probes that are stable and nuclease-resistant for tumor diagnosis in real biological systems.     

室内养殖管角螺幼体的生长特性

在室内养殖条件下,研究了水泥池养殖管角螺幼体的生长特性.结果显示:初孵稚螺早期壳高与螺重的生长速度都很快,旬增长率最高时分别达到186.7%、313.2%,以后生长逐渐减慢.壳高呈对数生长L=21.494lnd+2.0343(R2=0.9783);螺重呈幂形生长W=0.0388d2.5069(R2=0.962);稚螺螺重与壳高之间呈幂函数W=0.0001L2.770 8(R2=0.9569).不同时期稚螺成活率达到80%以上,壳高长至21.9mm以上,幼螺死亡逐渐减少,成活率均保持在91.6%～99.7%.不同时期的出肉率差别不显著,均达到50%以上.     

含氨基安替比林基的芳氧乙酰基硫脲的合成

合成了7个新的含氨基安替比林基的芳氧乙酰基硫脲类化合物(5a～5g),其结构经^1HNMR,IR和元素分析确证。室内生物活性测试结果表明部分5对某些真菌具有较高的抑菌率,其中5a对黄瓜灰霉的抑菌率达到92．45％。     

Biological activities from andiroba (Carapa guianensis Aublet.) and its biotechnological applications: A systematic review

Carapa guianensis is a tree from Meliaceae family traditionally known as andiroba that has a wide range of biological properties, including therapeutic effects, antioxidant activities, insecticidal and repellent effects that can be used in biotechnological approaches to medicine, agriculture, and cosmetic products. Therefore, we aim to explore the biological activities exhibited by this species and their respective biotechnological applications of interest. For this, a systematic review was carried out following the PRISMA guidelines dated from 1993 to 2022 through the Scopus, Web of Science and Agricultural Research Database (Base de Dados da Pesquisa Agropecuária - BDPA), screened for biological activity/bioactive compounds. A total of 129 studies were included in the PRISMA flow analysis. Biological properties and major bioactive compounds, as well as biotechnological approaches could be identified. The biological activity from C. guianensis could be observed in different vegetative parts through diverse methods of extractions. These activities are mainly due to the unsaturated fatty acids and bioactive compounds, such as the limonoids and a small fraction of phenolic compounds. Gedunin-type limonoids, like gedunin and its derivatives, represent the class of compounds that show the highest bioactivities in different applications.